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Fig.3 shows an interface between solid Si and liquid AI(-Si) alloy. The solid-liquid interface is straight along {111} planes of Si Fig.4 shows the interface between the solid Si and the liquid Al-Si at higher resolution. The interface is parallel to the (111) plane of the solid Si and atomically straight with a transition layer. Fig.4 (b) shows the intensity profile across the solid-liquid interface. Fig. 5 shows results of image simulations obtained by assuming that the transition layer as a mixture of partially solidified Si on the crystal surface and the liquid state. This layer was modeled by an additional atomic layer on top of the Si-{ 111} surface, as schematically shown in Fig.5(a). The trial thickness of the transition crystalline layer in the viewing direction was varied from 0.77 to 3.1nm to fit the experimental image, as shown in Fig.5(b), where the total thickness was assumed to be 5nm. The thickness of the crystalline part of the transition layer was estimated to lie between 1.5 to 2.3nm. Fig.6 shows dynamical behavior of a solid Si/Al(-Si) alloy liquid interface during crystal growth. The solid-liquid interface is travelling from right to left. Fig.7 shows the intensity profiles across the solid-liquid interfaces shown in Fig.6. In (a) the interface is at position 1. In (b), 1130 sec later, it has advanced to the position 2. The contrast of the atomic columns in the region between 1 and 2 is lower than that of the solid matrix (at the right side of 1) but higher than that of the liquid (at the left side of 2). This suggests that this region between 1 and 2 is a mixture of solid and liquid. In other words, atoms in this region are in a halfmolten state. In (c), the solid-liquid interface has advanced to position 3. Again, the lattice images between positions 1 and 3 are fainter than the region at the right side of 1. It is only 5/30sec later that the contrast of this transition region becomes comparable to that of the solid matrix. The velocity of the solid-liquid interface in this particular event is estimated to be approximately 20nm/sec.

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crystalline Al

Fig.1 Electron microgrps andthee rresponding diffraction patterns, respectively, of pure Al before and after melting.

FIg.2 Asequence of the processes of meting of an Al particle.

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Al-Si liquid

Fig.3 A low-magnification micrograph of an interface between solid Si and liquid AI(-Si) alloy.

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AI-Si liquid

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Fig.4 A high resolution image of the interface between solid Si and liquid Al-Si (b) Intensity profile across the S/L interface.

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Fig.5 (a) Model structure used for the image simulation. (b) Projection of the model structure and simulated images.

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Fig.6 Dynamical behavior of a S/L interface.

Fig.7 Intensity profiles of the S/L interfaces shown in Fig.6.

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Fig.8 shows a series of electron micrographs taken during melting ofAl-Cu alloy. Below the melting point the alloy consisted ofa typical eutectic sructure composed